fix doxygen brief in subzero header files

src/IceAssemblerX86Base.h

 //===- subzero/src/IceAssemblerX86Base.h - base x86 assembler -*- C++ -*---===//
 //
 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Modified by the Subzero authors.
 //
 //===----------------------------------------------------------------------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
-// This file defines the AssemblerX86 template class for x86, the base of all
-// X86 assemblers.
+/// \file
+/// \brief Defines the AssemblerX86 template class for x86, the base of all X86
+/// assemblers.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICEASSEMBLERX86BASE_H
 #define SUBZERO_SRC_ICEASSEMBLERX86BASE_H
 
 #include "IceAssembler.h"
 #include "IceDefs.h"
 #include "IceOperand.h"
 #include "IceTypes.h"
@@ skipping 1035 matching lines @@
   emitUint8(0x66);
 }
 
 } // end of namespace X86Internal
 
 } // end of namespace Ice
 
 #include "IceAssemblerX86BaseImpl.h"
 
 #endif // SUBZERO_SRC_ICEASSEMBLERX86BASE_H